This invention relates in general to a lifting apparatus and, in particular, to an apparatus for lifting and transporting a plurality of large containers.
More specifically, but without restriction to the particular use which is shown and described, this invention relates to a lifting apparatus having a grappler system to secure a stack of containers for lifting and transporting. The apparatus of the invention is capable of accommodating a stack consisting of a number of containers having a height greater than the height of the crane. The grappler system is adapted to engage the lower two containers in the stack in a manner, such that the bottom container may be released, while maintaining support of the containers above the released one.
In the transportation industry, certain types of containers have been developed, which are sometimes referred to as "intermodal" systems. Such trailers form unitized containers fitted to be interchanged between a truck, in which it forms a trailer therefor, and a ship or railroad car. The design of such containers has evolved into well-known standardized forms, such as IASO or Matson containers and the like. Each of these containers employ corner castings at each upper and lower corner to define sixteen apertures, which have been heretofore selectively engaged by such components as hooks or pins and the like for lifting the container. A typical gantry crane engages suitable holes in the corner casting and lifts a container, after it is removed from a train or ship, for example, and transports the container to a storage area, or directly to a truck, or alternatively, from the storage area to a truck and so forth. The conventional designs for such gantry cranes are only capable of lifting a single container at a time and can not accommodate the lifting and transporting of a plurality of containers in a stack for efficiency of operation.
Because of space limitations, transporting schedules, and considerations of economy, it is conventional for several transit containers to be stacked together in a storage area, for example, for a period during exchange between vehicles and/or vessels. As a result of design limitations of conventional cranes, it is only possible to move one container at a time to form such stacks. Moreover, existing cranes can carry only one container over a stack of three or four containers high, because no design in the prior art permits handling of containers above the top of the equipment. In view of the foregoing deficiencies, it is obvious that known cranes can only pick-up the top container of any given stack of limited height and must return to completely remove every item from a stack.
Known lifting equipment also suffers from limitations of operative versatility. For example, no cranes are available which can lift a stack of containers and release one of the containers as desired without interferring with the support of the remaining items. Prior apparatus are also designed so that the top beam or structure limits the height at which a container can be lifted over the stack, and thus, the number of items to be stored on top of each other.